1. Field of the Invention
This invention relates to automatic transmissions having multiple input clutches, but no torque converter for driveably connecting an engine and the transmission. More particularly, the invention pertains to such transmissions in which the kinematic arrangement includes epicyclic or planetary gearing rather than layshaft gearing.
2. Description of the Prior Art
Automatic transmissions for transmitting power between an input and an output, either over a continuously variable range of speed ratios or in discrete step changes among speed ratios, have associated with them several sources of parasitic losses, which adversely affect fuel economy. These losses are associated with a torque converter, open friction clutches and brakes, hydraulic pump, and gear meshes.
To improve fuel economy in a motor vehicle having an automatic transmission, an automated dual clutch transmission can be used to eliminate or substantially reduce all of these parasitic losses except gear mesh losses.
A dual clutch transmission consists essentially of two transmission units. One of the transmission units produces odd-numbered speed ratios; the other transmission unit produces even-numbered speed ratios. While operating in an odd numbered gear, synchronizers or couplers can be moved to configure the transmission for the next even numbered gear. A shift is then accomplished by releasing the clutch associated with the odd numbered gear while applying the clutch associated with the even numbered gear.